1. Field of the Invention
The present invention relates to a liquid discharge head for discharging a liquid.
2. Description of the Related Art
An example of the liquid discharge head, popularly used recently is an ink jet head. In general, the ink jet head includes a recording element substrate serving as a liquid discharge substrate for discharging the liquid, and an ink supply system for supplying such recording element substrate with an ink as a liquid.
Also such ink jet head is available in a tank-replaceable type in which an ink tank and an ink jet head are made detachable, and in an ink jet head cartridge type in which an ink jet head part and an ink container part, containing ink, are constructed integrally.
In the following, a conventional ink jet head will be described with reference to FIGS. 9A and 9B. The description will be made on an example of a color cartridge, for executing printing by discharging inks of yellow, magenta and cyan colors.
An ink jet head cartridge 601 illustrated in FIGS. 9A and 9B has a form in which an ink jet head portion, including a recording element substrate 702, and an ink container portion 709, containing ink, are integrally constructed. Within the ink container portion 709, provided is an ink supply path portion for supplying the ink jet head portion with the ink.
The recording element substrate 702 is equipped with a heater, as an element for generating energy for ink discharge, and a wiring for transmitting electric energy supplied from an unillustrated ink jet recording apparatus. On the recording element substrate, provided is a flow path constituting member, including a flow path for supplying the heater with the ink and an ink discharge port for discharging the ink.
In such conventional recording element substrate, the flow path constituting member includes discharge port arrays 703, 704, 705 for discharging inks of three colors of yellow, magenta and cyan.
Besides, the ink jet head 601 is equipped with an electric wiring tape 706, for transmitting electrical signals from the ink jet recording apparatus to the recording element substrate 702. The recording element substrate 702 receives the electrical signals from the ink jet recording apparatus, through external signal input terminals 707.
The recording element substrate 702 is electrically connected, at two end faces of the recording element substrate 702, with the electric wiring tape 706, and such electrical connecting portions are covered by a sealing material 708 and are protected from the ink.
Now a general construction around the recording element substrate 702 of the ink jet head portion will be described with reference to FIG. 10.
FIG. 10 is a cross-sectional view along a line C-C in FIG. 9A. Referring to FIG. 10, a recording element substrate 801 is supported on a support substrate 802. The support substrate 802 includes an ink supply opening 803, for supplying the recording element substrate 801 with the ink, contained in the ink container portion 709 of the ink jet head 601. The support substrate 802 is formed by molding and grinding a material such as alumina or the like, in order to adhere and fix precisely the recording element substrate 801.
Also on the support substrate 802 and around the recording element substrate 801, adhered is a support plate 804 having an aperture in which the recording element substrate 801 can be accommodated. The support plate 804 is formed by a material same as that of the support substrate 802. On the support plate 804, the electric wiring tape 706 is fixed and supported. A gap between a lateral face of the recording element substrate 801 and a lateral face of the support plate 804 is sealed by a sealing material 805 such as a resin. One of the reasons for such sealing is protect the lateral cut face of the recording element substrate 801 from the ink.
In another general example, the support substrate 802 and the support plate 804 illustrated in FIG. 10 are made of a resin. Such construction provides an advantage of inexpensive production, though the precision of adhesion of the recording element substrate 801 is lowered in comparison with the construction utilizing alumina or the like.
As the sealing material 805, a thermosetting resin that can be relatively easily handled in the production process is commonly adopted.
The construction described above with reference to FIG. 10 is disclosed in Japanese Patent Application Laid-Open No. H10-044420.
However, the construction illustrated in FIG. 10 involves the following drawbacks.
At first, there will be described drawbacks encountered when alumina is employed for the support substrate 802 and the support plate 804 illustrated in FIG. 10.
A thermosetting resin is employed for the sealing material 805 for sealing the periphery of the recording element substrate 801. Therefore, the sealing material 805 has a linear expansion coefficient generally higher than in the recording element substrate 801 utilizing a silicon substrate or in the support substrate 802 and the support plate 804 utilizing alumina. The sealing material 805 of the thermosetting resin is generally cured at a high temperature such as 100° C. or higher, and generates a curing shrinkage when the resin cured at the high temperature returns to the normal temperature. Also, the resin further deforms in the shrinking direction, for example when left in a low-temperature environment. In such case, the recording element substrate 801, the support substrate 802 and the support plate 804 also shrink, but a tensile stress is generated in a direction indicated by arrows in FIG. 10, because of the difference in the linear expansion coefficient from that of the sealing material 805. As a result, a defect such as a cracking of the recording element substrate 801 may be generated by such stress.
This phenomenon becomes a trouble in producing the recording element substrate of a lowered strength, which results for example by minimizing the size of the recording element substrate for the purpose of cost reduction.
Next, there will be described other drawbacks encountered with the support substrate 802 and the support plate 804 illustrated in FIG. 10.
The recording element substrate 801 is generally prepared with a silicon substrate. For this reason, the support substrate 802 formed by a resin, on which the recording element substrate 801 is adhered and fixed, has a linear expansion coefficient significantly larger than that of the recording element substrate 801. Therefore, in the case that the recording element substrate 801 is exposed to a temperature environment, extremely different from the temperature at which the recording element substrate 801 was fixed to the support substrate 802 of resinous material, the recording element substrate 801 is subjected to a deformation stress of the resin and may cause defects such as a deformation or a breakage.
In order to solve this problem, it is conceivable to form a beam structure in the ink supply opening 803 of the support substrate 802, thereby increasing the rigidity of the support substrate 802. In such construction, however, when the recording element substrate 801 is adhered and fixed to the support substrate 802 by an adhesive material, an excessive adhesive material may flow out along the beam and may enter the ink supply opening 803 provided in the recording element substrate 801. In a worst situation, an ink discharge port provided on the recording element substrate 801 may be clogged.